Selina Concise Solutions for ICSE Class 9 Biology Chapter 7 Respiration In Plants

Exercise 1

Question A:
Answer: 1. (c) in which glucose is broken down into pyruvate
2. (b) Stomata and lenticels
3. (d) Baker’s yeast
Respiration is a biological process where cells break down sugar to release energy. This first step of breaking down glucose happens in the cytoplasm and is common to all types of respiration.
Teacher's Tip: Think of glucose as "crude oil" and pyruvate as "refined petrol" that the cell can actually use.
Exam Tip: Always remember that stomata are in leaves, while lenticels are found on the bark of woody stems.

Question B.1:
Answer: Respiration is an essential life process for all living organisms. Therefore, plants also respire all day and all night.
Unlike photosynthesis, which needs sunlight to occur, respiration is a 24-hour activity. This continuous process ensures that the plant always has the energy needed for growth and cell repair.
Teacher's Tip: Plants "breathe" all the time, just like humans do, even when they are sleeping!
Exam Tip: If a question asks when plants respire, always write "all the time" or "day and night" to get full marks.

Question B.2:
Answer: (a) ATP
(b) Respiration
(c) Fungus
(d) Glycolysis
(e) Oxygen
(f) Soda lime
These terms represent the key components and chemical stages of the respiration process. ATP is particularly important as it acts as the "energy currency" for every living cell.
Teacher's Tip: Remember "Glyco" means sugar and "Lysis" means breaking; so Glycolysis is just "sugar-breaking."
Exam Tip: Learn the full form of ATP as it is a very common one-mark question.

Question B.3:
Answer: (a) False. Aerobic respiration of one mole of glucose yields 38 ATP.
(b) False. Anaerobic respiration in plants yields ethanol.
(c) True
(d) False. All leaves of a green plant normally respire aerobically at night.
Correcting these statements helps clarify the difference between aerobic and anaerobic respiration. Aerobic respiration is much more efficient because it produces significantly more energy molecules from the same amount of food.
Teacher's Tip: Think of Aerobic as "High Energy" (38 ATP) and Anaerobic as "Low Energy" (only 2 ATP).
Exam Tip: When a question asks to correct a false statement, always rewrite the entire sentence correctly.

Question C.1:
Answer: The energy liberated in respiration is stored in the form of ATP inside the cells. Some part of it is lost as heat to the surroundings.
ATP molecules act like tiny batteries that store energy for the cell to use later. While most energy is saved, the heat produced is why living things often feel warm.
Teacher's Tip: Imagine ATP as a fully charged phone battery ready to power the "apps" (functions) of the cell.
Exam Tip: Mention both "stored energy (ATP)" and "heat loss" for a complete answer.

Question C.2:
Answer: During day time, both photosynthesis and respiration takes place in green plants. Evolution of CO₂ is an indicator to demonstrate respiration in living organisms. CO₂ produced during respiration in plants gets utilized during photosynthesis and thus, there is no evolution of CO₂. Therefore, it is difficult to demonstrate respiration in green plants as there is no evolution of CO₂ during day time.
During the day, plants are busy recycling the gases they produce internally. Because the CO₂ from respiration is immediately used for making food, we cannot easily measure it coming out of the plant.
Teacher's Tip: Think of the plant as a "Zero Waste" factory during the day, using its own exhaust as raw material.
Exam Tip: Use the term "utilized" to explain why CO₂ doesn't appear to leave the plant during daylight.

Question C.3:
Answer: Respiration is said to be the reverse of photosynthesis due to the following reasons:
1. In respiration, the organic food is broken down into its inorganic compounds, i.e., CO₂ and H₂O, while in photosynthesis the organic food is synthesized from its inorganic components, i.e., CO₂ and H₂O.
2. In respiration, CO₂ is given out, while in photosynthesis CO₂ is consumed.
3. In respiration, O₂ is consumed, while in photosynthesis O₂ is released or evolved.
4. In respiration, energy is liberated, while in photosynthesis energy is absorbed.
These two processes form a perfect cycle that keeps life balanced on Earth. Photosynthesis builds up energy-rich food, while respiration breaks it down to release that energy for life activities.
Teacher's Tip: Photosynthesis is like "Cooking food," and Respiration is like "Eating food" to get energy.
Exam Tip: To score full marks, present your answer point-by-point, comparing the two processes directly.

Question C.4:
Answer: Tilling makes the soil porous and airy. The underground parts of the plants get sufficient amount of oxygen for respiration. In this way, tilling helps the crops to grow faster.
Roots need to "breathe" just as much as leaves do to stay healthy and strong. By loosening the dirt, farmers ensure that air can reach deep into the ground where the roots are growing.
Teacher's Tip: Tilling is like opening a window for the roots so they can get fresh air.
Exam Tip: Use the word "porous" to describe how tilling changes the soil structure.

Question C.5:
Answer: ATP: Adenosine triphosphate
ADP: Adenosine diphosphate
These molecules are the primary energy carriers in all living organisms. When an ATP molecule loses one phosphate group to become ADP, it releases a burst of energy for the cell to use.
Teacher's Tip: "Tri" means 3 phosphates (Full charge), and "Di" means 2 phosphates (Low charge).
Exam Tip: Memorize the spelling of "Adenosine" and "Triphosphate" carefully for spelling accuracy.

Question C.6:
Answer: Cell respiration cannot occur in any organism at a temperature of about 65°C because the enzymes involved in respiration become inactivated at high temperatures.
Enzymes are protein "workers" that speed up chemical reactions, but they are very sensitive to heat. If it gets too hot, these proteins lose their shape and can no longer do their jobs.
Teacher's Tip: Think of enzymes like plastic tools; if they get too hot, they melt and stop working.
Exam Tip: Always identify "enzymes" as the specific part of the cell that fails at high temperatures.

Question C.7:
Answer: (a) Lenticels
(b) Cytoplasm
(c) Glucose
(d) Photosynthesis, respiration
(e) Pyrogallate of potash
(f) KOH (caustic potash)
These specific terms help us identify the structures, chemicals, and processes related to plant biology. For instance, chemicals like KOH are used in lab experiments to specifically absorb carbon dioxide.
Teacher's Tip: KOH is a "CO₂ sponge" - it soaks it right up in experiments.
Exam Tip: Note that "Lenticels" are the openings on the stem, similar to stomata on leaves.

Question D.1:
Answer: Oxidation of organic food particularly carbohydrates in living cells to release energy is called respiration.
Similarities between respiration and burning:
1. Both require oxygen
2. Both produce energy
3. Both result in the formation of CO₂ and water
Differences between respiration and burning:
Respiration
1. Occurs in a series of chemical steps
2. Carried out by enzymes
3. Biochemical process
4. Energy is liberated in the form of ATP and some heat
5. No light energy is produced
6. Cellular process
7. Occurs at body temperature
8. No supply of heat energy is required
9. The organic compound is oxidized to carbon dioxide and water.
Burning
1. Occurs in a single step
2. Carried out by heat
3. Physico-chemical process
4. Energy is liberated in the form of heat and light
5. Light energy is produced
6. Non-cellular process
7. Occurs at high temperature (at ignition point)
8. Supply of heat energy is required
9. The organic compound initially chars and later burns, producing a flame.
While both processes release energy by using oxygen, respiration is a controlled and "slow" process that happens inside living cells. Burning is much faster and more violent, releasing energy as light and intense heat.
Teacher's Tip: Respiration is like a "controlled campfire" in your cells, while burning is like a "wildfire."
Exam Tip: When distinguishing between the two, highlight that respiration produces ATP while burning does not.

Question D.2:
Answer: Difference between aerobic and anaerobic respiration in plants:
Aerobic respiration in plants
1. Also called oxybiotic respiration
2. Proceeds in the presence of oxygen
3. Occurs in mitochondria
4. Complete breakdown of glucose
5. End-products are carbon dioxide and water
6. Large quantity of energy is liberated (38ATP) from one mole of glucose
7. Occurs normally throughout the life
Anaerobic respiration in plants
1. Also called anoxybiotic respiration
2. Proceeds in the absence of oxygen
3. Occurs in cytoplasm
4. Incomplete breakdown of glucose
5. End-products are ethyl alcohol and carbon dioxide
6. Small quantity of energy is liberated (2ATP) from one mole of glucose
7. Occurs temporarily for short periods
Aerobic respiration is the standard way plants live, providing them with high amounts of energy. Anaerobic respiration is a "backup plan" used only when oxygen is not available, such as in waterlogged soil.
Teacher's Tip: "An-aerobic" simply means "without air (oxygen)."
Exam Tip: Remember the specific end products: CO₂ and H₂O for aerobic; Ethyl Alcohol and CO₂ for anaerobic.

Question D.3:
Answer: (a) Experiment demonstrating that germinating seeds produce heat.
1. Take two thermos flasks ‘A’ and ‘B’.
2. Take about 200 bean or pea seeds and soak them in water for more than 24 hours.
3. Divide the seeds into two equal groups. Kill one group of seeds by boiling them and then, wash them with dilute formalin to prevent bacterial decay. Place the live germinating seeds in flask A and the killed one in flask B.
4. Insert a thermometer in each of the flasks and plug their mouths with cotton wool. Note the initial reading in the thermometer.
5. After few hours, the thermometer in flask A will show a higher reading indicating that the germinating seeds produce heat. There will not be any rise in the temperature of flask B.
(b) Experiment demonstrating that germinating seeds give out carbon dioxide.
1. Take two flasks ‘A’ and’ B’.
2. Place some wet cotton wool at the bottom of both the flasks.
3. Place some soaked seeds of pea in flask A and an equal number of boiled or dead seeds in flask B. Add some carbolic acid to flask B to prevent the growth of bacteria on dead seeds.
4. Cork the flasks and keep them undisturbed for few days.
5. After few days, the seeds in flask A will have germinated and the seeds in flask B do not show any signs of germination.
6. The gases in each of the flasks are then tested by removing the cork and tilting the flask over a test tube containing limewater and then shaking up the test tube.
7. The expected CO₂ present in flask A will turn limewater milky showing that germinating seeds give out CO₂, while the gas in flask B will show no effect on limewater.
(c) Experiment demonstrating that germinating seeds can respire even in total absence of air.
1. Take few soaked and peeled off pea seeds and push them into the mouth of a test tube filled with mercury and inverted in a beaker of mercury. The seeds will float to the top and will be completely surrounded by mercury.
2. After few days, the level of mercury falls and the presence of some gas in the test tube can be detected.
3. Add some KOH to the test tube. The gas present in the test tube will be absorbed and the level of mercury will again rise showing that the gas was CO₂. Hence, we can prove that germinating seeds respire even in the total absence of air.
These experiments prove three vital facts: respiration releases thermal energy, produces carbon dioxide gas, and can happen even without oxygen. By using "killed seeds" as a control group, we ensure that the changes we see are only because of the life processes in the living seeds.
Teacher's Tip: In biology, a "Control" group (the dead seeds) is used to prove that nothing else is causing the result.
Exam Tip: When describing the CO₂ test, always use the specific phrase "turns limewater milky."

Question D.4:
Answer: (a) Lenticels help the stem to participate in respiration.
(b) Stomata help the leaves to participate in respiration.
(c) Root hairs help the roots to participate in respiration.
Different parts of the plant have specialized openings to ensure gas exchange happens everywhere. This allows oxygen to reach the innermost cells of the roots, stems, and leaves.
Teacher's Tip: Every part of the plant has its own "nostrils" for breathing!
Exam Tip: Match the structure to the plant part: Stomata-Leaf, Lenticel-Stem, Root hair-Root.

Question E.1:
Answer: (a) Five flasks (A-E) are having different plant parts for observation.
(b) Limewater absorbs CO₂ present in the flasks. If CO₂ is produced, limewater turns milky.
(c) All the five flasks (A-E) containing plant parts will show respiration and thus, the tubes containing limewater will turn milky. The flask F does not contain any plant part. So, there is no respiration and hence, there is no change.
(d) Set-up F acts as a control for the experiment, where all the conditions are similar except for the plant part, which is missing.
(e) It can be concluded from this experiment that CO₂ is produced during respiration.
This wide-scale experiment shows that every part of a plant—flowers, leaves, and roots—is constantly respiring. By comparing them all to the empty Flask F, we prove that the CO₂ is coming from the plant material itself.
Teacher's Tip: Flask F is the "Control" because it shows what happens when nothing is added.
Exam Tip: Be sure to explain why the limewater changes (due to CO₂ gas).

Question E.2:
Answer: (i) (a) 6H₂O (b) C₂H₅OH
(ii) (a) Aerobic respiration; (b) Anaerobic respiration
(iii) Reaction (a) can be completed only in the presence of oxygen, while reaction (b) can be completed in the absence of oxygen.
Reaction (a) produces water and lots of energy, which is standard for most living things. Reaction (b) produces alcohol (C₂H₅OH) and occurs only when oxygen is missing.
Teacher's Tip: C₂H₅OH is Ethanol, the same alcohol used in hand sanitizers!
Exam Tip: Use the chemical formula C₂H₅OH to describe the byproduct of anaerobic respiration in plants.

Question E.3:
Answer: (a) Potassium hydroxide solution is kept in test tube X and Y to check the presence of CO₂, as KOH can absorb CO₂, if it is produced.
(b) When the process of respiration takes place in test tube X, the O₂ present in the test tube is consumed. The CO₂ produced due to respiration is absorbed by the KOH present in the test tube. Hence, a space is developed due to consumption of oxygen and hence, the coloured water rises in tubing 1.
(c) In test tube Y, boiled peas soaked in disinfectant are kept because the boiled seeds are dead and cannot respire. Therefore, the process of respiration does not take place in test tube Y.
(d) Respiration is the cause of the above rise.
(e) The catabolic process of releasing energy from simple sugars for carrying out life processes is called respiration.
This experiment helps us "see" respiration happening by measuring the change in air pressure. As the seeds use up oxygen and their CO₂ is removed by KOH, water is sucked into the tube to fill the empty space.
Teacher's Tip: The water rise is like someone sipping through a straw; the seeds "sip" the oxygen, creating a vacuum.
Exam Tip: Clearly state that KOH absorbs the CO₂ so we can measure the oxygen loss accurately.

Question E.4:
Answer: (a) The experiment was set up to study that CO₂ is given off from living plant material which performs respiration.
(b) Soda lime is kept in bottle ‘A’ so as to check the (presence of) passage of CO₂ present in bottle ‘B’. This is because soda lime has a tendency to absorb CO₂ present in air.
The limewater present in bottle ‘B’ shows that no CO₂ is entering bottle C with the air passing through bottle C.
(c) The bottle ‘D’ having limewater will show that CO₂ is produced due to respiration taking place in bottle ‘C’ having germinating seeds in it. Due to the CO₂ produced in bottle C, the limewater turns milky, which passes through bottle ‘D’.
(d) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38ATP (Energy)
(e) The bottle ‘C’ when covered with black cloth will have no scope for photosynthesis. Hence, only the process of respiration can be observed.
(f) By introducing a thermometer in bottle ‘C’, the change in temperature is checked or observed. If respiration takes place, there will be a rise in temperature and if there is no rise in temperature, no respiration occurs. Therefore, a three-holed rubber stopper and a thermometer were introduced.
By using black cloth, we stop the seeds from doing photosynthesis, which would use up the CO₂ we are trying to measure. The thermometer acts as a final proof that living processes are active, as they always release some heat energy.
Teacher's Tip: Soda lime is the first "filter" to make sure only clean, CO₂ -free air reaches the seeds.
Exam Tip: Be ready to write the full chemical equation for aerobic respiration, including the 38 ATP.